Optical networks are presently in use in many buildings. Despite their inherently high bandwidth capacity relative to systems based on electrical cables, such networks must often be expanded to keep up with the ever increasing bandwidth demands of improved computer and telecommunications systems. Network expansion typically involves the addition of network components that are remotely located from the central processing unit of the network. In particular, the growth of wireless communication has increased the demand for wireless interfaces with existing office and building-sized optical networks. Around these wireless interfaces, picocells or so-called hot spots are typically created for high-speed wireless data communication. Such interfaces can take the form of transponders that serve as remote antennas which in turn are connected to a central head-end.
Electrical power is necessary to operate the opto-electronic semiconductor devices present in the added network components, whether they take the form of transponders or some other remotely-added equipment. As optical fibers cannot transmit electrical power, some other means for providing electricity to the added components is necessary. The simplest way would be to add additional electrical power lines to the network. However, the remote location of the added components often makes the addition of such power lines difficult and expensive. Another solution might be the use of cable that combines both optical fibers and an electrical power line. While such a solution would be less expensive than the separate installation of electrical power lines, it would still necessitate the addition of electrical cables.
Passive picocell designs have been proposed using electro-absorption modulators (EAMs). In some of these designs, the EAM is biased by an electrical signal. This can be derived from light received from a remote source of optical power via an optical fiber that is converted into electrical power. Unfortunately, EAMs are relatively expensive, being manufactured in small numbers. Worse yet, EAMs require the use of single mode optical fiber in order to function, whereas most small scale, short distance optical networks use multimode fiber in order to reduce overall system cost. Hence, such a solution again requires (in most cases) the replacement of at least some optical fiber of the system, and is disadvantageously expensive due to the cost of EAMs.
Clearly, what is needed is a system to add new components, such as transponders, to an existing optical network which would not require the separate installation of electrical power lines, or the replacement of any of the existing optical fiber. Ideally, such a system would be relatively easy and inexpensive to implement, and completely compatible with the existing network infrastructure. Finally, such a system should also be capable of implementing whole new building-sized networks utilizing inexpensive multi-mode optical fiber.